I'm not sure "only twice as bad" paints an accurate picture.
- Herd immunity is much harder. Calculated as 1 - 1/r0 where r0 is defined in relation to transmissibility. So if r0 = 3 that's ~66% need to be immune to stop the virus. If r0 = 6 that's 83% needed, much higher threshold.
- The virus is only getting more deadly. A preprint study found delta has "120% greater risk of hospitalization, 287% greater risk of ICU admission and 137% greater risk of death"[1]
Also 225% more transmissible is 3x more unless I'm doing my math wrong?[2]
Right, and that's where vaccine efficacy comes into play. If r0 is 6 and HIT is 83.3%, but efficacy is only 90%, then you actually need about 93% vaccinated.
And for herd immunity, what matters is transmission, and the vaccine efficacies for asymptomatic infection are pretty low; 50-60%. So mathematically impossible without severe lockdowns and/or improved vaccines that are better at preventing transmission.
But I've been operating under the assumption that while vaccination won't prevent you from infection, it is still highly effective (90%+) at reducing symptoms, even with Delta. I'm certainly open to learning if this is false, however. I've just seen statistics that over 95% of people hospitalized are unvaccinated.
There are many efficacy numbers. mRNA does help against infection but efficacy is apparently low, like 50-60%. Makes sense because they weren't really developed with that in mind.
Efficacy goes to 60-80% for symptomatic, over 80% for serious/hospitalization, and mid 90% for death. I think.
Herd immunity happens long before we are all infected. Less than 40% of the US population is completely unvaccinated, which means we can open up more without overwhelming hospitals. That does put the unvaccinated at increased risks, but the general public is seemingly unwilling to continue lockdowns to protect people choosing not to be vaccinated.
If ~85% is needed for herd immunity then we could be rapidly approaching that point. Though specific locations would likely have outbreaks even if it was less of a concern nationally.
With an R0 of about 6 for the Delta variant, herd immunity won't provide a meaningful level of protection for most people. Herd immunity works with less contagious diseases because susceptible individuals can go their whole lives without exposure. But with SARS-CoV-2 now being endemic worldwide we'll all eventually get exposed, it's just a question of when. So the smart move is for everyone to protect themselves by getting vaccinated and actively treating co-morbid conditions like obesity, diabetes, hypertension, and hypovitaminosis D.
Any further lockdowns at this point cause far more harm than benefit.
They can prevent hospitals from being overwhelmed. Opening or not opening schools are one case where local communities are going to adjust based on the rates of hospitalization.
There's math you can do to roughly judge impact of partial vaccination. If R0 is six, and you're looking at hospitalization, estimate vaccine efficacy for Delta at around 90% (I've seen estimates above and below that).
Taking your estimate of a 60% vaccination rate:
6 * (1 - (.6 * .9)) = 2.76
2.76 is the effective Rt, which is far above 1, so no, that is not enough to open up more without eventually overwhelming hospitals.
Natural immunity from catching COVID, and other (inherently temporary) mitigation measures like masks/distancing/lockdowns would bring that Rt down further. But clearly what is best is more vaccination.
2.76 assumes normal conditions, social distancing literally changes the equation.
Mask use for example pushes that down. It’s easier to get below 1 with a 50% vaccination rate than a 0% rate. Meaning we can open up more without overwhelming hospitals.
That's pretty much what I said in my last line. The problem is, "opening up more" generally tends to mean things like less masking and less social distancing. So to the extent that Rt is pushed down by mitigation measures, Rt gets pushed back up when those mitigation measures end.
The advantage in my mind is you can avoid the most costly mitigation strategies.
Unfortunately, vaccination rates are age dependent so opening schools is a very high risk activity. Children are at low risk for COVID but they would be a major vector for transmission as everyone under 12 is unvaccinated.
That’s quite regional. Nationwide there is still plenty of ICU beds available, and presumably if it gets bad enough hot spots will respond appropriately.
By moving people with covid to other states, or importing medical personnel and equipment. Do so aggressively enough and you can keep capacity available.
And then you'll eventually realize: having thousands of people getting intensive care at the same time until everyone either had it or died from it is moraly not acceptable. Why do you come up with the idea that it's better to increase capacity rather than using large scale vaccination efforts?
I think there's am R0 for initial strain and then ranges for the other variants. I thought it was in Wikipedia but either it's been edited out or I saw it elsewhere.
What I recall (so huge grain of salt here) was R0 at 2.3 for initial strain then around 2x for Alpha and another 2-3x for Delta. Not. Great.
"Furthermore, measles's reproductive number estimates vary beyond the frequently cited range of 12 to 18.[15] The NIH quote this 2017 paper saying: "[a] review in 2017 identified feasible measles R0 values of 3.7–203.3"
